The present invention relates to a three way servo valve whose piston is displaced by a symmetrical fluidic amplifier, and which is at one end also subjected to the pressure of a consumer conduit.
In a servo control valve of this type according to the prior art, the pump pressure acts at one end, and the consumer conduit pressure acts on the other end of the piston. The pressure of the consumer conduit is applied to a portion of the respective end face of the piston. The piston is in equilibrium when the opposing axial forces are equal. In this position of equilibrium, the piston is in an initial position, and the consumer conduit is separated from the pump conduit, and from the discharge conduit. When the control pressure produced by a fluidic amplifier is reduced, the respective obtained consumer pressure is increased, and vice versa. In the valve according to the prior art, the end face to which the pump conduit pressure is applied has the same area as the end face to which the consumer conduit pressure is applied, and difficulties arise when the consumer pressure is to be equal to the pump pressure. In this event, the control pressure must be zero which can be obtained only by stopping the flow of control fluid through the fluidic amplifier, which requires a very expensive construction.